+1 - Good question. It looks like opinions vary, so far. I'd be interested to know if / how much this varies from implementation to implementation (ie, how much is one implementation affected versus another).
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D. LambertFeb 15 '11 at 16:15

11 Answers
11

I don't know how it works with this lens, but I've seen charts for Pentax's in-body stabilization system where the data shows that contrary to conventional wisdom I.S. gives a (decreasing but still there) benefit up until rather high shutter speeds, at which point it doesn't matter (and doesn't make things worse).

If you have the camera on a very steady tripod, though, off is probably better. On a lightweight, wobbly tripod, it may be different.

It's also important to keep in mind that the stabilization takes time to engage and "settle" — typically half a second or so after you half-press the shutter button. If you have it on, make sure to allow that time.

Even on a wobbly tripod your IS should be off (unless the lens is capable of detecting it is tripod mounted) as the bracing of the camera body against a (mostly) solid object can cause a vibration feedback loop (this is usually mentioned in instruction manuals although I guess the effect would be less pronounced with 'in body' stablisation as the vibrations occur closer to the secured mass)
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JamWheelFeb 15 '11 at 15:19

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Speaking of Pentax and a tripod: If you use a self-timer or remote (as you should in those situations), Pentax DSLRs automatically disengage stabilization and enable mirror lock-up for you. It's one of the details I enjoy which speeds things up automatically.
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ItaiFeb 15 '11 at 15:20

Itai -- on my Pentax SLR (a K-7), the SR indicator is the little hand symbol, not the green hex, which is just for focus confirmation. I've rolled back your edit....
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mattdmFeb 15 '11 at 18:15

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Why is off better on a stable tripod if the data you've seen shows that it's never detrimental to the photo? Also, do you have a link to that data?
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brianFeb 15 '11 at 20:38

@JamWheel, do you have a citation for the feedback loop scenario?
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brianFeb 15 '11 at 20:39

I heard about IS affecting the Bokeh. The reasoning seems sound to me: the optical path (optical IS) is varied or the lens plane is moved (sensor IS) leading to a different distribution of the typical "lens sharpness" compared to a non-stabilized lens. This will perhaps be more visible because you expect a uniform distribution of bokeh on a far-away background and at the edges.

It would certainly be worth testing this in a controlled setup. No, I'm not going to do anything about it ;)

If you search around here and elsewhere you'll find lots of arguments for and against when one should/shouldn't use IS/VR/SR. The remarkable thing about so many words exercised is that it's so easy to test and decide for yourself, your own use, and your own standards. Take some pictures in the same way with and without it. Look at them closely. Can you tell the difference for better or worse? Do you care? There's your answer.

For example, I've tested a couple of my (Nikon) lenses on a tripod with VR operating, and not. Couldn't tell any difference at 100%. That's good enough for me. I still turn it off because the delay it causes can be a little annoying, but if I forget, no worries.

And another thing, seeing as I'm here. That 1/focal length rule? Completely bogus. To think that so many variables involved in hand-holding steadiness could be reduced to such a trivial formula? It really doesn't withstand any scrutiny. Curiously, it's another myth that digital photography makes very easy to test for oneself, yet so few seem to. It's funny how the quoted rule didn't change when so many folks started using less than 'full frame' sensors, though.

What kind of images do you shoot? If you always take pictures in bright light at 1/250 of a second or faster and you have very steady hands, then IS may not be helping you. On the other hand, if you're usually taking pictures in low light (say 1/25 or 1/50 of a second or even longer) or you don't have a good stance, then IS is probably making your pictures a lot better. If you are moving back and forth a lot between those two scenarios (I know I do), then just continue to leave IS on because, at least in my experience, the benefit to the low-light pictures is far greater than any potential harm to the brightly-lit pictures.

Of course, since you're getting conflicting advice here, I'd recommend running your own experiment. On the next sunny day, go out and take some photos with the same settings (aperture, ISO, etc.; you'll probably get a more accurate test if you use your normal settings to figure out the exposure and then take the test pictures in manual mode, so exposure settings don't change between pictures) you normally use, both with and without IS, and compare the results (and please report back here when you're done!).

As someone who uses the IS capability of the EF 100-400mm L series lens a lot, I can say that it is something you need to choose to use. IS is a tool, and it is designed to solve a specific problem. Its not the ubiquitous hammer that can apparently solve every problem known to man, so you need to be explicit about the cases where you use it.

IS is intended to improve the performance of a lens when hand held, in situations where hand-holding is either not possible, or difficult. If you have enough light to follow the Focal Length Reciprocal rule, which states that a shutter speed of 1/FocalLength at a minimum (without IS) should be used to capture a sharp photo, then turn off IS. If you do not have enough light to capture a sharp photo at a proper exposure with the reciprocal rule, then you should enable IS before you increase the ISO. The IS system of the 18-55 might get you 1-2 stops of additional hand-holdability, while better IS (such as that on the 100-400mm) may get you up to 3-4 stops additional hand-holdability. That means you could reduce the shutter speed up to two stops lower than the reciprocal rule would dictate, and get a clear shot. At 55mm, that would mean a shutter speed of 1/15s (+2s tops) should be sufficient. At 400mm, that would mean a shutter speed of 1/100s (+3 stops).

If you are unable to get a shot by enabling IS, then its finally time to crank up your ISO. As a general rule, I try to keep my ISO as low as possible. In the case of shooting wildlife and birds, I tend to set my ISO to Auto, and unless I'm photographing in bright daylight, I turn IS on in mode 1 (stabilization in both horiz and vert planes.)

There's some good information in here... I'm failing to see the one part I'm looking for, though: why you'd actually want to turn it off, and under what conditions. Perhaps an edit is coming? :)
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lindesFeb 18 '11 at 21:43

@lindes: The conditions for turning it on (if you usually keep it off) or turning it off (if you usually keep it in) are subjective. The simple point is: do you need it? If you don't need it, its probably best to turn it off, since leaving it on CAN introduce undesirable outcomes. For one, it takes a moment to activate, and if it "activates" during an exposure, you can get blurry or double images as it suddenly moves from its centered position.
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jrista♦Feb 19 '11 at 4:16

I guess I'm just wanting your answer to more directly target this line from the original question: "Except the battery draining, is there any evidence that using IS the image quality will be reduced?" -- because I imagine you have plenty of good stuff to say on that front, I'm just seeing something different. :) More stuff like "if it "activates" during an exposure, you can get blurry or double images" -- put that sort of stuff in your answer, perhaps with more detailed explanation and/or links. I'd write my own answer, but honestly I don't know the details all that well.
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lindesFeb 19 '11 at 10:44

In most circumstances it's safe to leave it on all the time, particularly if it's implemented in a smart kind of way.

For image stabilisation to work it needs to detect, at high speed, fine rotational movements. However no such detection is ever 100% accurate - there's always an error margin which translates to very fine, low level movements. This never matters in normal situations where you'd use it, because in reality holding the camera by hand at 1/250th or slower will always generate far, far more movement than any inaccuracy of the image stabilisation system. So it's a net gain.

When the camera is locked down completely with a tripod, however, then there should be no movement of the camera. So not only is IS not needed, but you wouldn't want the inaccuracy of its rotational detection system to generate tiny movements at all. Even though any motion will be less than hand-holding at a normal shutter speed, if you had the ability to have less chance of blur, you'd take it wouldn't you?

Some cameras are smart enough to detect they're likely on a tripod and won't move the IS system, just like some cameras will automatically turn off IS for shutter speeds of 1/500 and faster. But it's kind of hard to find out this information about any particular lens or body.

@JamWheel - I suppose the rest of the article goes on to talk about more specifically when it is and isn't needed. Shutter speed, surrounding environment, and the subject all factor into this decision.
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TomFeb 15 '11 at 19:26

Image quality can be adversely affected if the camera is on a tripod, or if the focal length is out of bounds of what the IS system "expects." For example, some cameras and/or lenses recommend disabling IS for macro photography. But in the tests I've tried, it hasn't made a significant difference and it's usually hard to see any degradation.

For me the big problem with Image Stabilization is that it takes a while to "wake up", if you just want to take a very quick picture of a fast moving object, chances are the first one will be blurred by the IS system, even when using a high shutter speed (e.g. 1/250 at 30mm).

At least that's how my Sigma 17-70 OS seems to behave.

I guess it's still better to leave it on all the time when "walking around". This way you don't have to remember to put it back on when lighting conditions change to low light.

I found myself a few times caught with IS off when I really needed it. It simply isn't a habit of mine to check this switch on a lens.

All in all I found myself to have many more "rescued" photographs due to IS being on, than ruined due to it misbehaving.

Image Quality will not be affected at all. The light still passes through the same piece of glass whether it is on or off.

You might get a feedback loop if you have the IS on whilst tripod mounted (unless the lens can detect it is tripod mounted) where the vibrations of the glass being moved by the IS system cause further vibrations but this causes a motion blur type effect and still wouldn't affect the image quality, rather the quality of the image...

Using IS in an environment where lots of vibrations are present (on an aircraft / car on a bumpy track) it can have an effect also.

Hmmmm. I think that in order for the answer to make any sense, you have to define what you mean by "image quality", which, on its face, would be synonymous with the term "quality of the image", which you set it in opposition to.
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mattdmFeb 15 '11 at 14:59

When referenced Image quality mostly refers to the technical aspects of the image quality (detail resolution, chromatic aberration etc) whereas the quality of the image would refer to whether the image is any good / is sharp / is well exposed.
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JamWheelFeb 15 '11 at 15:16

Sharpness is usually considered to be a technical aspect of image quality....
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mattdmFeb 15 '11 at 18:26

In this case by "is sharp" I mean, has been taken correctly by the user (quality of the image ie "is it a good image?"), rather than the sharpness the equipment is capable of delivering "what is the image quality produce by the equipment combination?".
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JamWheelFeb 15 '11 at 18:46